1. Field of the Invention
The invention generally relates to the field of mobile communications, and more particularly, to methods for speeding up location registration procedures, enabling the mobile communication devices to switch away from a problematic tracking area to another normal-service tracking area for performing location registration procedures to obtain mobile communication services.
2. Description of the Prior Art
In a typical mobile communications environment, a user equipment (UE) may communicate voice and/or data signals with one or more service networks. The wireless communications between the UE and the service networks maybe in compliance with various wireless technologies, such as the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA 2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, and others.
In general, a UE is configured to camp on a cellular station with best reception, and perform a location registration procedure via the cellular station to register itself to the service network to which the cellular station belongs. Specifically, during the location registration procedure in GSM and UMTS, the UE transmits the registration information, such as the identification of the UE and the current location area of the UE, to the service network. During the location registration procedure in LTE, the UE transmits the registration information, such as the identification of the UE and the current tracking area of the UE, to the service network. According to the registration information, the service network may determine whether to accept the location registration request from the UE. For example, the service network may determine the subscription status of the UE according to the identification of the UE, or may determine whether the service capacity is enough for serving the UE according to the current location of the UE. After that, the service network may reply to the UE with the result of the location registration request. If the location registration request is accepted, the UE may obtain mobile communication services, such as the voice and/or data services, from the service network.
Note that, the operator of the service network may periodically practice maintenance or update of the cellular stations belonging to a specific location area or tracking area. In this situation, the UEs remaining in the specific location area or tracking area may fail to register themselves to the service network and may not be able to obtain mobile communication services from the service network. According to the release 5 to 7 of the 3GPP TS 24.008 specification (referred to herein as the TS 24.008 specification), the release 11 of the 3GPP TS 24.301 specification (referred to herein as the TS 24.301 specification), and releases 6 and 7 of the 3GPP TS 23.122 specification (referred to herein as the TS 23.122 specification), when the location registration request of a UE is rejected by a service network, the UE is configured to retransmit the location registration request associated with the same tracking area for a predetermined number of times until the registration request is accepted. However, if the UE is still rejected after retransmitting the location registration request for the predetermined number of times, the UE is then configured to release the Radio Resource (RR) connection, i.e., the connection between the UE and the service network, and enter the Mobility Management (MM) idle mode. When in the MM idle mode, the UE has to wait for a period of time before being ready to re-perform the location registration procedure or perform a Public Land Mobile Network (PLMN) search procedure. Disadvantageously, whether re-performing the location registration procedure or performing a PLMN search procedure, a great deal of time is required for the UE to successfully register itself to the service network and obtain mobile communication services. As a result, real-time user experience may be hard to guarantee due to the break-off of the mobile communication services.